Means for preventing flashback in powder melting torches



I Oct. 25, 1966 A. T. CAPE 3,281,078

MEANS FOR PREVENTING FLASHBACK IN POWDER MELTING TORCHES Filed Sept. 9, 1965 INVENTOR.

F 1 9. 5 ARTHUR 1'. CAPE ATTORNEYS United States Patent 3,281,078 MEANS FOR PREVENTING FLASHBACK IN POWDER MELTING TORCHES Arthur T. Cape, Monterey, Calif., assignor to Powder Melting Corporation, Monterey, Calif., a corporation of California Filed Sept. 9, 1965, Ser. No. 486,183 6 Claims. (Cl. 239-85) This application is a continuation-in-part of my copending application, Serial No. 332,200, filed December 20, 1963, now abandoned.

The invention relates, as indicated, to means for preventing flashback in powder melting torches, but has reference more particularly to the incorporation of such means in torches of the type described, for example, in my Patent No. 3,194,501.

In torches of the aforesaid type, powder is dropped by gravity into a torch chamber into which a combustible mixture of oxygen and fuel gas'i flows, and the powder is then carried by such mixture to a nozzle to provide a powder melting flame at the tip of the nozzle.

The passage of the combustible mixture through said chamber creates a partial vacuum within the chamber, but the presence of powder in the chamber causes a decrease in this partial vacuum, so that if there is any obstruction in the system downstream of said chamber, there is a tendency for the flow of the combustible gas mixture vto be reversed. As a result, the flame will tend to travel back to the chamber, where an explosion will occur, and if gas has collected in the hopper from which the powder flows into the chamber, a dangerous explosion may occur. This recession of the flame into the interior of the torch is commonly known as a flashback or backfire.

The present invention has as its primary object the provision of means of an extremely simple nature, which can be easily incorporated in the torch structure, and which is effective to prevent such flashback.

Other objects and advantages of my invention will be apparent during the course of the following description.

In the accompanying drawings forming a part of this specification, and in which like numerals are employed to designate like parts throughout the same,

FIG. 1 is a fragmentary side elevati-onal view of a powder melting torch embodying the invention, with portions broken away to illustrate certain features;

FIG. 2 is a cross-sectional view, taken on the line 22 of FIG. 1;

FIG. 3 is a view, on an enlarged scale, of a portion of FIG. 1, but showing a modification of the invention;

FIG. 4 is a cross-sectional view, taken on the line 4-4 of FIG. 3, and

FIG. 5 is a cross-sectional view, taken on the line 5-5 of FIG. 3.

Referring more particularly to FIGS. 1 and 2 of the drawings, there is disclosed a torch having a body 1, to the forward end of which a nozzle 2 is secured, as by a coupling nut 3. A torch butt fragmentarily indicated by reference numeral 4 in FIG. 1, is secured to the torch body by an adapter or coupling 5 and a nut 6. The butt 4 is provided adjacent its rear end with knobs (not shown) which operate oygen and fuel gas valves, for controlling the fi-ow of such oxygen and fuel gas through the torch in accordance with conventional torch design.

A combustible mixture of oxygen and fuel gas is carried into the torch body by means of an injector nozzle 7, which discharges the combustible mixture into a chamber 8 in the body 1, the mixture flowing from the chamber 8, through a passageway 9 of reduced cross-section in the body 1, the mixture flowing from this passageway into the nozzle 2 to provide a powder melting flame at the tip 10 of the nozzle 2.

3,281,078 Patented Oct. 25, 1966 The body 1 is provided with an opening 11 through which powder is dropped by gravity from a hopper 12 into the chamber 8 of the torch body in a manner described in my aforesaid patent, to which reference may be had for further details.

The passage of the combustible mixture through the chamber 8 creates a partial vacuum in this chamber and provides an aspirator action for withdrawing powder from the chamber. The flow of powder depends partly on gravity and partly on suction of the aspirator, but the flow of powder is substantially proportional to the combustible mixture flow, because the suction of the aspirator depends upon the volume of combustible mixture discharged by the injector nozzle 7.

The presence of powder in the torch chamber 8 causes a decrease in the partial vacuum within this chamber, so that if there is any obstruction in the system downstream of the chamber 8, as, for example, an accumulation of carbon or other matter on the tip 10, there is a tendency for the direction of flow of the gas to be reversed. As a result, the combustible gas mixture accumulates in the chamber 8 and in the hopper 12 and in the passageway through which the powder drops into the chamber 8. This accumulated combustible gas mixture is ignited by the receding flame, causing an explosion which can result in serious injury to the operator and/or destruction of the torch, and even when there is no explosion, a bubbling of the powder in the hopper occurs, which disrupts the operation or use of the torch.

For the purpose of preventing such flashback, I attach to the body 1 of the torch, at a point downstream from the chamber 8, and preferably from the passageway 9, a flap valve 13, of a material such, for example, as silicone rubber, metal foil, or the like, the valve being attached or anchored to the body 1, as at 14, as by means of epoxy glue or like cement, or the flap valve may, in fact, be secured to the body 1, at the point 14, as by means of a mechanical hinge (not shown).

The valve 13, in the absence of passage of the gas stream through the passageway 9, is self-closing, that is to say, it closes the exitend of the passageway 9, as shown in solid lines in FIG. '1.

When the torch is in use, the gas stream, along with the powder entrained therein, opens the valve, as by lifting it to a position approximately as indicated by the broken lines in FIG. 1, in which position, the valve does not, in any way, obstruct the flow of gases and powder.

If, for the reasons already stated, the flow of gas is reversed, and is of such a nature as to create the possibility of a flashback, the valve 13 will close immediately and prevent the entry of the flame into the passageway 9 or chamber 8.

The element 13 thus constitutes a flap valve, which is highly effective to prevent flashback in torches of the character described. The shape or contour of this valve may be varied, as will be readily understood.

In FIGS. 3, 4 and 5 of the drawings, there is illustrated a modification of the invent-ion, in which a short tube 15, of silicone rubber or like flexible or resilient material, is provided, this tube having a flange 16 at its rear end, and a forward end having a closed slit 17. The slit 17 is created by molding the tube 15 in such manner that the walls at the forward end of the tube are normally collapsed upon each other.

The tube 15 is positioned within the torch in such a manner the flange 16 thereof is clamped between a seat 18 of the torch and the rear end 19 of the nozzle 2, and the tube extends into the rear end of the nozzle.

In the absence of passage of the gas stream through the passageway 9, the slit 17 is closed, as shown in solid lines in FIG. 3.

When the torch is in use, the gas stream, along with the powder entrained therein, causes the slit 17 to open, so that the forward end of the tube assumes a substantially tubular or cylindrical condition, as shown in broken lines in FIG. 3, in which condition, the tube does not, in any way, obstruct or impede the flow of gases into the nozzle. If, for the reasons already stated, the flow of gas is reversed, and is of such a nature as to create the possibility of a flashback, the valve, or rather the slit 17, will close immediately, and prevent entry of the flame into the passageway 9 or chamber 8.

The tube 15 thus constitutes a self-closing valve, which is highly effective to prevent flashback in torches of the character described. The shape or contour of this valve may be varied, as will be readily understood.

It is to be understood that the forms of my invention, herewith shown and described, are to be taken as preferred examples of the same, and that various changes may be made in the shape, size and arrangement of parts thereof, without departing from the spirit of the invention or the scope of the subjoined claims.

Having thus described my invention, I claim:

1. In a powder melting torch, a torch. body having "a chamber therein into which a combustible gas mixture 4. ing flashback in said torch, said means comprising a valve disposed in said torch body downstream fiom said chamber and upstream from the nozzle, said valve being inherent-ly-self-closin-g, but openable during passage of said gas mixture through the torch, and being inherently selfclosable on cessation of flow of gas in said forward direction through the torch and being closable in response to reversal of the direction of flow of said gas mixture through the torch on flashback.

2. A torch, as defined in claim 1, in which said valve is a flap valve.

3. A torch, as defined in claim 1, in which said valve is a tubular valve having a self-closing slit at one end thereof.

flows, a nozzle secured to the tor-ward end of said body and through which said combustible gas mixtu-re' flows from said chamber to provide a powder melting flame at the tip of the nozzle, a powder hopperniounted on and disposed above said torch body, -a passageway extending from said hopper to said chamber through which powder is dropped by gravity from said hopper to said chamber in a direction substantially perpendicular to the direction of flow of said comlbust-ible gas mixture through said chamber, the flow of said combustible gas mixtu-rethrough said chamber creating a partial vacuum providing an aspirator action for withdrawing powder fromfthe chamber, and the improvement comprising means for prevent- 4. A torch, as defined in claim 1, in which said torch has a passageway of reduced diameter downstream of said chamber, and said valve is disposed at the exit end of said passageway. a I

5. A torch, as defined in claim 4, in whichfsaid ,valve is a flap valve. 7 v I v 6. A torch, as defined in claim '4, in which said valve comprises a tubular member having a self-closing slit at one end thereof.

References flirted by the Examiner UNITED STATES PATENTS 192,100 6/1877 Walker et al 239 571 2,418,200 4/1947 Smith 239435 3,034,731 5/1962 Chapin 239 571 3,172,605 3/1965 Brooks 239- 3,194,501 7/1965 Cape 2398,5 3,204,875 9/1-965 Langstroth 209- FOREIGN PATENTS 233,799 12/1944. Switzerland.

EVERETT W. KIRBY, Primary Examiner. 

1. IN A POWDER MELTING TORCH, A TORCH BODY HAVING A CHAMBER THEREIN INTO WHICH A COMBUSTIBLE GAS MIXTURE FLOWS, A NOZZLE SECURED TO THE FORWARD END OF SAID BODY AND THROUGH WHICH SAID COMBUSTIBLE GAS MIXTURE FLOWS FROM SAID CHAMBER TO PROVIDE A POWDER MELTING FLAME AT THE TIP OF THE NOZZLE, A POWDER HOPPER MOUNTED ON AND DISPOSED ABOVE SAID TORCH BODY, A PASSAGEWAY EXTENDING FROM SAID HOPPER TO SAID CHAMBER THROUGH WHICH POWDER IS DROPPED BY GRAVITY FROM SAID HOPPER TO SAID CHAMBER IN A DIRECTION SUBSTANTIALLY PERPENDICULAR TO THE DIRECTION OF FLOW OF SAID COMBUSTIBLE GAS MIXTURE THROUGH SAID CHAMBER, THE FLOW OF SAID COMBUSTIBLE GAS MIXTURE THROUGH SAID CHAMBER CREATING A PARTIAL VACUUM PROVIDING AN ASPIRATOR ACTION FOR WITHDRAWING POWDER FROM THE CHAMBER, AND THE IMPROVEMENT COMPRISING MEANS FOR PREVENTING FLASHBACK IN SAID TORCH, SAID MEANS COMPRISING A VALVE DISPOSED IN SAID TORCH BODY DOWNSTREAM FROM SAID CHAMBER AND UPSTREAM FROM THE NOZZLE, SAID VALVE BEING INHERENTLY SELF-CLOSING, BUT OPENABLE DURING PASSAGE OF SAID GAS MIXTURE THROUGH THE TORCH, AND BEING INHERENTLY SELFCLOSABLE ON CESSATION OF FLOW OF GAS IN SAID FORWARD DIRECTION THROUGH THE TORCH AND BEING CLOSABLE IN RESPONSE TO REVERSAL OF THE DIRECTION OF FLOW OF SAID GAS MIXTURE THROUGH THE TORCH ON FLASHBACK. 